Powder forming apparatus



1, 1964 N. DEMAKAY 3,143,918

POWDER FORMING APPARATUS Filed June 28 1961 2 Sheets-Sheet 1 20 I8 2| 5 3| m 60 Bio 2 3| 28 22 mm FIG.6

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POWDER FORMING APPARATUS Filed June 28, 1961 2 Sheets-Sheet 2 T I .4 A 37 69 7o I 68 l (I l ll'l'll'l AAA 72 73 as in; u

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NICOLAS DEMAKAY ATTORNEYS United States Patent 3,143,918 POWDER FORMHNG APPARATUS Nicolas de Maltay, Rio de .laneiro, Brazil Filed June 28, 1961, Ser. No. 120,209 3 Claims. (Cl. 86-4) This invention relates to apparatus used in the manufacture of powder, and particularly to apparatus for manufacturing flake nitrocellulose powder grains, and is a continuation-in-part of my copending application Serial No. 721,707, filed March 17, 1958, now abandoned, which was a continuation-in-part of my application Serial No. 637,273, filed January 30, 1957, now abandoned.

The manufacture of satisfactory flake type powder for small firearms is diflicult because the powder must have a high burning velocity and must be composed of uniform grains so as to have identical ballistic properties. One method of accomplishing this result is to incorporate soluble salts, such as sodium chloride or sodium nitrate, in the colloided powder prior to the powder extruding step and then to dissolve the salts from the powder so as to leave a porous structure of nitrocellulose which burns rapidly. Another method is to incorporate oxidizing compounds in the powder, such as nitrates, chlorates and the like. The major problems encountered in the practicing of either of these methods are first: the extreme difliculty of distributing the salts uniformly throughout the colloided nitrocellulose, and second: the undissolved salts remaining in the pores will result in an irregular burning of the grains of nitrocellulose and corrosion of the firearms. Another of the major problems is that of obtaining uniformly sized and shaped flakes.

One of the objects of this invention is to provide an apparatus which will produce a uniform powder having a high burning velocity.

Another object of the invention is the provision of means for controlling the powder graining mechanism so as to produce uniform discs or grains which have substantially identical forms.

It is particularly diflicult to produce a powder having uniform powder grains because of variations in flow through the passages or passage means in the die due to the changes in viscosity caused by friction heat. This is one of the reasons why continuous extrusion devices of the helical screw type, such as the ones used in the plastic industries, are not suitable for this operation. Also, in screw type feeders, the material must be sufficiently soft so that it can be pushed through the forming passages for otherwise it will slip relative to the screw and thus will not be fed uniformly through the passages. When it is too soft, the cutting blades, described hereafter, may distort the flakes so that they become elongated. The screw feeder does not positively move the material to the die because of the possible slippage between the material and the surface of the screw. A piston positively feeds material through the die.

In one aspect of the invention, so as to overcome these difliculties and in order to prevent variations in the operating speed of the piston, which must be correlated with the blade or knife rotation, the grain forming apparatus may include a die cylinder for receiving the colloided powder, preferably single base, and a reciprocable cable piston employed in the die cylinder. Located at one end of the die cylinder is a die having a plurality of passages therethrough. Means are provided for urging the piston into the die cylinder to extrude the colloided powder through the passages. A plurality of revolving blades are mounted adjacent the bottom of the die and the bottom of the passages to cut the extruded threads into discs of the desired thickness. The speed of the knives or blades can be set as needed. Thus, by using a piston, the powder can be made sufliciently hard so that when it is extruded and cut, uniform flakes will result. Means for maintaining the speed of the stroke of the piston constant for a constant speed of rotation of the blades is required so that there will be a constant feed of the powder relative to the knife blades. As a further aspect, the length of the passages adjacent the center of the die can be made longer than the length of the passages adjacent the walls of the piston, so as to compensate for the slower velocity adjacent the Walls due to friction between the powder and the walls of the die cylinder.

These and other objects, features and advantages of the invention will become apparent from the following detailed description and drawings which are merely exemplary.

In the drawings:

FIG. 1 is a side elevation, with parts broken away for clarity, of one form of apparatus of the invention, some of the control means being shown schematically;

FIG. 2 is a view similar to FIG. 1 showing another form of the invention;

FIG. 3 is an enlarged cross sectional View of one form of die which can be used in accordance with the invention;

FIG. 4 is a schematic View of one type of constant speed control that might be used;

FIG. 5 is a fragmentary enlarged view of the front of the speed controller; and

FIG. 6 is a sectional View taken along line 6-6 of FIG. 4.

One form of the apparatus of the invention, as shown in FIG. 1, includes a hydraulic piston 11 which is driven downwardly by fluid under pressure fed through pressure line 12. A pressure gauge means 13 can be connected to the pressure line to indicate the pressure of the fluid operating the hydraulic press. Any conventional means, such as weight 14, can be provided for urging the piston upwardly when there is no pressure in the hydraulic cylinder. Die cylinder 15, which contains the colloided nitrocellulose, has a die 16 mounted at its bottom end. The die, which has passages 17 therethrough, is preferably arranged so that the passages in the center are longer than the outer ones. Such will serve to counteract or compensate for the slower flow velocity at the outer passages due to the frictional force on the colloided powder mass at its outer periphery and thus result in a uniform flow of the colloided powder at the bottom portion of the die or through the passages in the die. Since the frictional force is small, the variation in the length of the openings will be very small, but in the interests of clarity, this variation has been exaggerated in the drawings.

In contact with or adjacent the flat bottom surface of the die adjacent the bottom of passages 17 are a plurality of blades or knives 18 mounted on shaft 19 for rotation therewith. The blades when operated at the proper speed in relation to the speed of the stroke of the piston will cut the extruded solution into thin discs or flakes of a uniform thickness and shape. As an example, for a powder of proper burning velocity, the discs should have a thickness of 0.1 millimeter or less since the largest grains of nitrocellulose preferably are 0.1 millimeter or less. The diameter of the discs preferably is from 0.5- 2.5 millimeters depending on the size of the openings in the die. Also, the discs should not be distorted when cut.

In one form, the colloided powder may contain at least 0.1% graphite which will act as a lubricant for the blades, thereby reducing friction and temperature.

The blades are constantly urged upwardly toward the bottom of the die by compression spring 20 which contacts the lower portion of the blades and flanged portion 21 of tubular body 22 in which shaft 19 is mounted. Shaft 19 is rotated at a velocity of over 200 r.p.m. by the driving shaft of motor 23, through a conventional bevel slow relative to the rotational speed of the blades.

gear arrangementshown schematically at 24, which is driven through a variable speed reducer 31a by motor 23. Speed reducer 31a may be of any conventional type, such as a Reeves type whereinthe variation in speed is accomplished by the relative movement of the sheavesof a pulley. Alternatively, other well known types of adjustable speed reducers may be used such as illustrated in FIGS. 4 and 6.

After the discs are cut by the revolving blades, they fall through chute 25 directly to an agitator tank 26 containing water or an aqueous solution'of alcohol and acetone for the purpose of removing the solvent from the discs. The ballistic properties of a given powder can be controlled by the grain size and the degree of porosity. The texture of the finished powder can be regulated by adjusting the temperature of the solvent within the range of 1 C. to 100 C., by varying the concentration of the solvent, and by varying the rotational speed of an agitator 27 in the tank. Fine pores are obtained at lower temperatures where osmosis controls the rate of removal of solvent, whereas larger pores are produced at higher temperatures where vaporization of solventfrom the powder is predominant. The finally formed discs flow out with the overflowing solvent and may later be coated with graphite or other suitable material as is well known in the art.

I The agitator tank 26 must be in close proximity to the revolving blades 18 so that the discs enter the aqueous solution immediately after their formation. If not, the discs will contract in size, thereby resulting in non-uniformity and also a reduction in the degree of porosity of the discs. This may be due at least partly at first to solvent removal from the exterior portions of the discs.

Since the thickness of the discs is governed by the speed of rotation of the blades and the speed at which the powder strands are emitted from the die, means must be provided for coordinating or' controlling the two speeds. One form of control means, as shown in FIG. 1, for coordinating these speeds will now be described. Details of one suitable form are illustrated in FIGS. 4, and 6.

A shaft 28 connected to one side of a speed or condition difference responsive mechanism 29 transmits to mechanism 29 an angular rotational speed signal proportional to the rotation of the revolving blades. The other side of mechanism 29 is connected with suitable speed responsive means, shown schematically at 30, which trans mits a speed signal proportional to the linear speed of the piston stroke to mechanism 29. The speed responsive means may be conventional such as shown in FIG. 2, to be described hereinafter. If the two speed signals transmitted to mechanism 29 are equal, the pointer 60 of the mechanism 29 is at rest and if the two speed signals differ, the pointer will swing either to the right or left depending on whether the piston speed is too fast or t2: example of gauge mechanism having a speed responsive portion is seen in US. Patent No. 2,709,843, such matching piston speed with another variable, such as temperature for which, of course, another speed input could be substituted. An example of a differential gear train speed comparing means is found on page 23, line 19 (FIG. 23) of Servomechanism Fundamentals, by Lauer et al., published by McGraw-Hill Book Company, Inc. (1947).

- Referring now to FIGS. 4, 5 and 6, motor 23 drives gears 24 through a conventional adjustable speed reducer 31a having bevel gears 50, 50 which are separable by means of a threaded shaft 51 operable by wheel 52. Nuts 53, 53 have yokes for adjusting the distance between the bevel gears, the gears being slidable on shaft 54. Mating bevel gears 55 are spring urged inwardly so as to maintain engagement with bevel gears 50, 50. Thus, the speed of shaft 56 relative to speed of shaft 57 will depend upon the relation of the bevel gears. A similar 'adjustable speed reducing gear 31 is provided. The differential speed difference indicating means 29 has a speed input from shaft 28 proportional to the speed of knives 18. Shaft 58 is driven by rack 59 or other conventional speed responsive means in proportion to the speed of piston 11. When the speeds of shafts 28 and 58 are the same, the responsive means is adjusted so that pointer 63' is centered. If the speeds vary, then the differential cage 61 will move in one direction or the other relative to the axis of shafts 28 and 58 to turn gear 62 and gear 63. Movement of gear 63 will turn pointer 60 so that it makes contact with either contact 64, 65 to adjust the position of valve'34 to control the hydraulic force exerted on piston 11. a

Due to impurities in the driving fluid and the leaking of gaskets, the speed of the piston stroke will rarely be constant, thereby causing the needle 60 of mechanism 29 to swing from its rest or null position.

Manually operated valve 32 may be set to provide bleed off fluid from line 12 for preliminary adjustment or for manual control, if needed.

The speed reducer 31 mounted between motor 23 and mechanism 29 is employed to adjust the angular rotational speed transmitted through shaft 28 to mechanism 29. As stated above, speed reducer 31a mounted between constant speed motor 23 and'th'e revolving blades is employed to adjust the rotational speed of the blades. The use of these speed reducers in conjunction with valve means 32 or 33 permits the operation of the device of the invention in the production of powder discs of any desired predetermined thickness which have substantially uniform characteristics.

Another form of control means utilizing the teachings of the invention is shown in FIG. 2, in which identical parts have the same reference numerals as in FIG. 1. In this form, the cutter speed is adjusted to the desired value by adjustment of speed reducer 31a, and since the speedof motor 23 is constant, the cutter speed will stay constant. Therefore, the piston speed must be kept constant to maintain the desired ratio betweenthe cutter speedand the piston speed. This can be conveniently achieved by converting the linear motion of the piston 11 and rack 34a into rotary motion by gear 35 driving a magneto, generator or speed signal producing means 36 through a proper reducer 37a, similar to speed reducers 31 and 31a of FIG. 1. The speed of the piston in terms of the signal produced or generated by magneto 36 may be indicated on a conventional condition responsive means 37. By manually regulating valve 38, the piston speed as indicated on the instrument can be kept relatively constant. If desired, the piston speed can be controlled automatically by condition responsive means 37, which in such instance may be of a type well known in the art. Condition responsive means 37 operates or controls a pneumatic or electric valve 39 to adjust the flow of fluid to the piston to keep the piston speed constant. Pneumatically operated valves controlled by various condition responsive means are known, for example, as shown in US. Patent No. Re. 21,804. One conventional arrangement is seen in FIG. 2 wherein the elected speed signal from magneto 36 is fed to coil 66. Armature 67 thereof positions flapper 68 relative to nozzle 69. Control air is fed through pipe 70 and restriction 71 to the nozzle 69, pilot valve 72 and feedback bellows 73 in the usual manner. The output of the pilot valve 72 will be proportional to the speed of the piston so that pneumatically operated valve 39 will be controlled thereby to bleed off hydraulic fluid so as to maintain the speed of piston 11 constant. The coordinated cutter and piston speed ratio can be chosen in accordance with the desired grain size and type of powder.

A slightly modified form of die is shown in FIG. 3. This die 16a, as well as the die of FIGS. 1 and 2, has longer passages 17a adjacent the center. However, no holes are provided in the central portion thereof, thereby minimizing, to an extent, the variation in the flow speed.

It is to be understood that details of construction can be varied without departing from the spirit of the invention except as defined in the appended claims.

What is claimed is:

1. Apparatus for producing disc shaped powder elements of uniform size from a colloided mass of powder and solvent comprising a reciprocable piston, a die cylinder containing the colloided mass, a die having a plurality of openings therein located at one end of said die cylinder, hydraulic means for urging said piston into said die cylinder to cause the colloided mass to be extruded through said openings, a plurality of revolving blades adjacent the bottom of said die which cut the extruded powder into thin discs, means for controlling said hydraulic urging means in response to the speed of the stroke of the piston and the rotational speed of said blades, said controlling means including speed difference responsive means which receives information as to any variation in a predetermined ratio between the speed of the stroke of the piston and the blade speed, speed adjusting means for the piston, and means for transmitting information relative to said variation from the speed difference responsive means to the speed adjusting means so as to change the speed of the stroke of the piston to conform said piston speed to said predetermined ratio relative to the blade speed.

2. Apparatus for producing disc shaped powder elements of uniform size from a colloided mass of powder and solvent comprising a reciprocable piston, a die cylinder containing the colloided mass, a die having a plurality of openings therein located at one end of said die cylinder, hydraulic means for urging said piston into said die cylinder to cause the colloided mass to be extruded through said openings, a plurality of revolving blades adjacent the bottom of said die which cut the extruded powder into thin discs, means for controlling said urging means in response to the speed of the stroke of the piston and the rotational speed of said blades, said controlling means including speed diiference responsive means which receives information as to any variation in a predetermined ratio between the speed of the stroke of the piston and the blade speed, speed adjusting means for the piston, means for transmitting information relative to said variation from the speed difference responsive means to the speed adjusting means so as to change 45 the speed of the stroke of the piston to conform said piston speed to said predetermined ratio relative to the blade speed, and an agitator tank means mounted in close proximity to the bottom of said die so as to receive the discs immediately after their formation, said agitator tank means having an agitator therein and being filled with an aqueous solution so that the solvent portion of the colloided mass contained in the discs is extracted leaving porous powder discs of substantially uniform size.

3. Apparatus for producing disc shaped powder elements of uniform size from a colloided mass of powder and solvent comprising a reciprocable piston, a die cylinder containing the colloided mass, a die having a plurality of openings therein located at one end of said die cylinder, said openings being longer adjacent the center of said die than they are adjacent the outer portion thereof so as to compensate for the reduced flow adjacent the walls of said die cylinder caused by the friction between said powder mass and said walls, means for urging said piston into said die cylinder to cause the colloided mass to be extruded through said openings, a plurality of revolving blades adjacent the bottom of said die which cut the extruded powder into thin discs, piston speed responsive means, revolving blade speed responsive means, means connected to both of said speed responsive means for maintaining the speed of the stroke of the piston in a constant predetermined ratio relative to the speed of the revolving blades, and an agitator tank means mounted in close proximity to the bottom of said die so as to receive the discs immediately after their formation, said agitator tank means having an agitator therein and being filled with an aqueous solution so that the solvent portion of the colloided mass contained in the discs is extracted leaving porous powder discs of substantially uniform size.

References Cited in the file of this patent UNITED STATES PATENTS 802,347 Aspinwall Oct. 17, 1905 899,577 Wadsworth Sept. 29, 1908 2,149,920 Kretchmer Mar. 7, 1939 2,401,236 Fielitz May 28, 1946 2,432,734 Doesken Dec. 16, 1947 2,436,201 Cole Feb. 17, 1948 2,622,273 Detwiler Dec. 23, 1952 2,740,705 ONeill Apr. 3, 1956 2,747,224 Koch et a1. May 29, d 

1. APPARATUS FOR PRODUCING DISC SHAPED POWDER ELEMENTS OF UNIFORM SIZE FROM A COLLOIDED MASS OF POWDER AND SOLVENT COMPRISING A RECIPROCABLE PISTON, A DIE CYLINDER CONTAINING THE COLLOIDED MASS, A DIE HAVING A PLURALITY OF OPENINGS THEREIN LOCATED AT ONE END OF SAID DIE CYLINDER, HYDRAULIC MEANS FOR URGING SAID PISTON INTO SAID DIE CYLINDER TO CAUSE THE COLLOIDED MASS TO BE EXTRUDED THROUGH SAID OPENINGS, A PLURALITY OF REVOLVING BLADES ADJACENT THE BOTTOM OF SAID DIE WHICH CUT THE EXTRUDED POWDER INTO THIN DISCS, MEANS FOR CONTROLLING SAID HYDRAULIC URGING MEANS IN RESPONSE TO THE SPEED OF THE STROKE OF THE PISTON AND THE ROTATIONAL SPEED OF SAID BLADES, SAID CONTROLLING MEANS INCLUDING SPEED DIFFERENCE RESPONSIVE MEANS WHICH RECEIVES INFORMATION AS TO ANY VARIATION IN A PREDETERMINED RATIO BETWEEN THE SPEED OF THE STROKE OF THE PISTON AND THE BLADE SPEED, SPEED ADJUSTING MEANS FOR THE PISTON, AND MEANS FOR TRANSMITTING INFORMATION RELATIVE TO SAID VARIATION FROM THE SPEED DIFFERENCE RESPONSIVE MEANS TO THE SPEED ADJUSTING MEANS SO AS TO CHANGE THE SPEED OF THE STROKE OF THE PISTON TO CONFORM SAID PISTON SPEED TO SAID PREDETERMINED RATIO RELATIVE TO THE BLADE SPEED. 